Fan opinion is somewhat worthless. Conforto has a career 124 wRC+ (meaning hes 24% abouve league average), he hits for power from the left side, he's serviceable defensively. Career OBP of .356. He's far and away the best fit for the Sox on the FA market.
He won't be super cheap, but you're getting hit a significant discount from what he'd have costed prior to 21. I think a deal similar to Yaz gets it done. 3-4 years at $15-18M AAV.